Environmental control systems are available which can control environmental parameters. An example environmental control system is a heating ventilation and air conditioning (HVAC) system, which may comprise one or more devices which are operable to heat, ventilate and/or air condition a premises. In some cases, HVAC systems or environmental control systems may be operable to provide only heating, ventilation air conditioning or humidity control, rather than a combination. Environmental control systems may comprise environmental control devices or appliances for controlling the environmental parameters, e.g. boilers, radiators, central heating systems, air conditioning units or dehumidifiers and/or humidifiers.
Thermostats, or environmental controllers, can be used to provide control commands to environmental appliances in order to influence or change environmental parameters or characteristics, such as the temperature or humidity. It is possible to provide control commands for environmental control systems by programming a schedule into a thermostat at a premises, for example by pressing buttons or interacting with a touch screen on the thermostat.
Thermostats may be connected to environmental appliances by wired connections and/or they may be connected wirelessly so that it is possible to send commands to the appliances. Some of these appliances may be able to influence an environmental parameter in more than one direction, for example a heat pump may be available both for providing cooling and heating (when operating in different modes), or a fan may be used in order to optimise both heating and cooling, as appropriate. Additionally or alternatively there may be more than one appliance which can influence an environmental parameter in the same manner, for example a gas furnace or boiler and a heat pump may both be available for increasing air temperature.